Green Gold :: Green Gold Alloy :: Green Gold Jewelry :: Green Gold Jewellery

Green gold is not really green, not in the grass sense of green, or the leaves sense either. Green gold normally appears as a very subtle, greenish yellow tint rather than what we would normally call green. Blending of silver and pure gold produces the colour tone found in green gold and that we call green gold alloy.

Green Gold Alloy

Green gold alloyis made by reducing the copper content from an alloy mixture and using just gold and silver.

Colour can be determined in terms of the component reflected light wavelengths it has using a CieLab color-measuring system.

There are three generally attributed green gold colour variations:

• Soft green gold
• Light green gold
• Green gold

An exploration of some differing metal combination in gold alloys that produce green gold's can be found below, but if you prefer to jump to the uses for green gold then:
Jump

Green gold was known to Lydians from around 2,900 years ago. They knew it as electrum. The ancient Greeks called it gold or white gold, as opposed to refined gold.

Electrum is an alloy of silver and gold (with trace amounts of copper etc.). It ranges in colour from pale to bright yellow (depending on the gold : silver ratio.

Electrum occurs naturally in Western Anatolia, Turkey, where today it is mined and produces from a 70:30 to 90:10 ratio gold : silver. This gives an insight into the minds of the ancient Lydians, who lived in the same geographical area, and to man himself.

Why?

How?

Well, the Lydians coinage has been found to be in the ratio from 45:55 to 55:45, gold:silver ratio.

How come it is so different to the naturally occurring electrum?

Well, they must have wanted to increase their returns by sullying the coinage down from the 90:10 ratio circulating locally, to one where they made more profit. Not too far removed from what we have seen throughout the ages. And it is no different today.

Electrum has also been produced artificially, but then it is only one of a large range of green gold alloys.

The greenish colour of green gold is achieved when raising the silver:gold ratio of the alloy.

Eighteen carat (karat) green gold usually contains a mix of 75%:25% gold:silver. Most green golds are very soft and generally used only in small amounts to highlight other gold colours.

But there are many other admixtures that achieve similar results colour-wise and better results hardness-, durability- and workability-wise. See the tables below for an idea of the many options available for green gold alloy production.

Green gold is, however, more malleable than red or yellow gold, but less durable.

The table above shows that with decreasing levels of silver in the green gold alloy, the colour tends away from a green colouration until at an alloy ratio of 50:25:25 gold(Au):silver(Ag):copper(Cu), the green colour disappears to a yellowish hue.

With the addition of Zinc (Zn), the greenish hue stays and other attributes that make this green gold more workable are introduced.

The table above shows a number of alloy constituent percentage variants that have zinc (Zn) included. With the percentages shown there is little difference in the green colour tone of the gold alloy.

With the addition of cobalt (Co) and iridium (Ir) further green gold alloys can be produced.

Again there is little variation in the green gold alloy colouration and there could be advantages in usability terms for the alloy when admixing the addition elements as shown in the table above.

Finally, with the addition of indium (In) we see that this element has no appreciable influence on the colour but again may have positive affects on other attributes that a gold alloy needs to be useful in jewellery manufacture.

The table above again shows that the greenish colour of the gold alloy with the elements shown, is not impaired.

The table below, however shows that the addition of cadmium (Cd) to an original combination of gold, silver and copper will give a more green hue to gold alloys.

Cadmium can be added to gold alloys in amounts up to 4% to achieve dark green colourations.

Cadmium is however toxic.

Green gold has been created by a patination technique on copper-containing carat golds in the range 15wt% to 67.5wt% copper.

This produces what is described as a thin ‘verdigris’ film on the surface.

A number of chemical mixtures are described to produce the green patina, many involving copper salts.

There is no known evidence that green gold jewellery production by patination is yet commercially available,

The classic mixture that produces green gold is an alloy of pure yellow gold and pure silver -- though, for rings, harder metals such as zinc are used to make the gold more durable. Green gold is most noticeable when it is used next to areas of yellow, white, and pink gold in jewellery items.

Traditionally, 18-karat green gold alloys have been used to provide a colour contrast to other alloys in multi-colored jewellery articles, such as bracelets, necklaces etc. Most existing 18-karat green gold alloys are based on the familiar gold-silver-copper combination, and typically contain high concentrations of silver.

Hand-made pieces of jewellery lend themselves well to having combinations of various coloured gold alloys including green gold alloys.

For more coloured golds see Gold Colours :: Gold Colors by Humagaia.

For the next in this series of gold colours see Gold :: Yellow Gold by Humagaia

For the previous in this series of gold colours see Gold :: Blue Gold by Humagaia

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